The proposed research will investigate the structure-activity relationship and mechanism of action for neonatal hemorrhage that has been reported to occur in neonates born to mothers receiving anticonvulsant drugs during pregnancy. The studies will measure in vitro prothrombin synthesis in liver from vitamin K deficient and normal rats treated with phenobarbital, phenytoin or primidone. The effects of phototherapy on in vitro drug metabolism of skin and liver from irradiated rats will be studied using hyperbilirubinemic and normal Gunn rats. The interaction of phototherapy, hyperbilirubinemia and a light sensitive drug, tetracycline, will also be studied in hyperbilirubinemic and normal Gunn rats. The effects of hyperbilirubinemia on reproduction will be investigated in the relatively infertila hyperbilirubinemic female Gunn rat.